The present invention relates to a method and apparatus for photothermal destruction of toxic organic compounds, and more particularly, to a process which utilizes high temperatures in combination with radiation exposure to induce a photochemical reaction which completely detoxifies a wide variety of toxic organic compounds.
Throughout the industrialized world, there is a growing concern over the impact of industry on the environment, specifically with regard to the increasing emission of contaminants into the atmosphere. Of additional concern is the clean-up of extensive damage already done to specific sites and of the widespread contamination of ground water. According to recent estimates, between 330 and 570 million tons of hazardous waste were generated between 1900 and 1980, and 290 million tons of waste are now produced annually in the United States. The level of concentration of such wastes pose health hazards to the general population.
One method of controlling hazardous waste disposal has been high temperature incineration. Incineration is capable of breaking down a wide variety of toxic materials into carbon dioxide, water, and simple mineral acids. However, this process is very expensive and is inappropriate for many applications such as soil and ground water cleanup. In addition, public concern over emission of undestroyed residual components, organic products of incomplete combustion, and off-gas streams laden with organic vapors, have led to regulations by the Environmental Protection Agency, which now requires that incinerators possess a destruction and removal efficiency of 99.99% for the principal organic hazardous components in a waste stream.
Another method proposed for treating large volumes of toxic organic wastes has been the use of solar radiation. Sunlight contains both infrared radiation, which can be used to heat the waste, and ultraviolet radiation, which can promote photochemical reactions. However, the unreliability of solar energy limits its use in detoxification processes.
As a result, other more reliable sources of radiation such as high intensity ultraviolet lamps have been employed. For example, Confer, U.S. Pat. No. 4,210,503, uses ultraviolet lamps to irradiate a gas stream containing vinyl chloride, forming less hazardous materials which are then absorbed in a scrubber. However, Confer does not utilize heat in combination with the radiation, which slows down the detoxification reaction and limits the treatment capacity of the process.
Legan, U.S. Pat. No. 4,045,316 discloses a process for decontaminating gaseous or vaporous streams of vinyl chloride in which the streams are exposed to heat and radiation. However, relatively low temperatures (i.e., nearly ambient) are maintained during the process, which may result in incomplete mineralization of the organic components.
Thus, while prior art processes have utilized either heat or radiation to destroy hazardous wastes, none of the processes have used a combination of intense heat and radiation. Although some processes disclose the use of slightly elevated temperatures as well as radiation, such slightly elevated temperatures are a physical requirement, e.g., for the purpose of preventing moisture condensation, and do not effectively aid in the detoxification process itself.
Further, many prior art processes, such as those described above, are limited to the detoxification of oxidizable contaminants.
Accordingly, there is still a need in the art for a process which uses concentrated radiation in combination with high temperatures to effectively destroy a large number of toxic organic wastes without producing any harmful byproducts.